All substances, ＿＿＿＿＿ solids, liquids, or gases, are made up of entirely atoms.

A.whether they     B.whether  C.whether are they     D.whether are

B


解析:

在帶有狀語從句的復合句中，如果從句與主句的主語一致，且從句中含有be動詞，則可以省略從句的主語及be動詞。此處從句中省略了they are。

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